In the related art, as a bearing used for a high-speed rotating body, a radial bearing is known which is used in a state of encircling a rotary shaft. As such a radial bearing, a radial foil bearing is well known which includes a thin sheet-shaped top foil forming a bearing surface, a back foil resiliently supporting the top foil, and a cylindrical bearing housing accommodating the top foil and the back foil. A bump foil, in which a thin sheet is formed in a wave sheet shape, is mainly employed as the back foil of the radial foil bearing.
As such a radial foil bearing, Patent Document 1, particularly FIG. 4 thereof, or FIG. 2 of Patent Document 2 discloses a structure including a bar-shaped locking member (a limiting member) which limits the movement of the back foil in the axial direction in order to prevent detachment of the back foil from the bearing housing.
In the structure of Patent Document 1 or 2, in order to fix the locking member to the bearing housing, two side surfaces (end surfaces in the axial direction) of the bearing housing are provided with engagement portions (engagement recesses, engagement grooves), and the engagement portions are engaged with engagement portions (engagement arms, engagement legs) of the locking member. The locking member holds the back foil, whereby the movement of the back foil in the axial direction is limited, and the detachment of the back foil from the bearing housing is prevented.
Patent Documents 3 to 5 disclose a radial foil bearing which includes a top foil (an upper foil) and a back foil (a back spring, an under foil).